In recent years, Blue-ray Discs and HD DVDs have been developed as next generation optical discs. As a molding material to be used for production of a Blu-ray Disc substrate or an HD DVD substrate, Patent Document 1, for example, discloses a polycarbonate resin composition for an optical information substrate containing a partial ester of saturated aliphatic acid carboxylic acid having 10 to 30 carbon atoms and polyhydric alcohol and a full ester of saturated aliphatic carboxylic acid having 10 to 30 carbon atoms and polyhydric alcohol mixed with a polycarbonate resin produced by an ester exchange method.
The polycarbonate resin composition in Patent Document 1 employs the polycarbonate resin produced by an ester exchange method. However, in the case where a substrate for an optical information medium such as a CD (compact disc) or a DVD is produced by using the polycarbonate resin produced by an ester exchange method, a difference in terminal groups of the polycarbonate resin to be obtained causes disadvantages such as a lower glass transition point than that of a polycarbonate resin obtained by an interfacial method so as to provide a short molding cycle or deformation of a substrate during releasing with increasing die temperature. Further, the polycarbonate resin produced by an ester exchange method has reactivity with a partial ester to be added, and a residual amount of the partial ester after pelletization tends to be reduced.
Meanwhile, in the case where burr or the like caused by charging of a substrate is adhered to the substrate in a step of producing a Blu-ray Disc substrate or an HD DVD substrate through injection molding, appearance failures called comets form on a Blu-ray Disc or an HD DVD. Formation of the comets causes problems in that defective phenomena such as error in reading of the Blu-ray Disc or the HD DVD occur.
Charging of the substrate taken out of an extruder causes adherence of fine resin burr derived from the extruder or suspended dust to a substrate surface after molding. The comets as used herein refer to streak defects formed from an inner periphery to an outer periphery of the substrate in a radius direction due to convex parts formed of the adhered products. In the case of a Blu-ray Disc, the comets form after formation of a reflective film on a Blu-ray Disc substrate surface through sputtering, vapor deposition, or the like and during formation of a transparent protective layer having a thickness of 0.1 mm by a spin coating method or the like by using a UV (ultraviolet light)-curable resin because flow of the UV-curable resin is inhibited by the convex part. In the case of an HD DVD Disc, the comets form during formation of a recording film on an HD DVD substrate by using an organic pigment by a spin coating method or the like in a similar manner to that of a conventional recordable optical disc such as a DVD-R because flow of the organic pigment is inhibited by the convex part.                Patent Document 1: JP-A-2004-331808        